1. Field of the Invention
This invention relates generally to electronic systems for testing electronic devices and more particularly to electronic systems which convert parallel input data signals into serial input data signals for testing electronic devices responsive to serial input data signals.
2. Summary of the Invention
In accordance with the present invention, an electronic system for testing an electronic device responsive to a serial input data signal comprises an oscillator for repetitively generating oscillator pulses at a selected repetition period, timing circuitry for counting oscillator pulses and for generating one or more input select signals indicative of the number or numbers of oscillator pulses counted, and multiplexing circuitry for receiving two or more parallel input data signals and for sequentially selecting each of the parallel input data signals in response to the input select signal or signals to generate the serial input data signal. The electronic device under test accepts the serial input data signal when it is synchronous with a data clock signal produced by a data clock signal generator responsive to oscillator pulses.
Preferably, the electronic testing system includes a data clock signal inhibitor for inhibiting the data clock signal after the multiplexing circuitry has selected each of the parallel input data signals a specified number of times so that the device under test no longer accepts the serial input data signal. The data clock signal inhibitor inhibits the data clock signal in response to one or more timing signals produced by the timing circuitry after it has counted a selected number of oscillator pulses.
The testing system may also include circuitry for generating a signal to initiate an auxiliary function further required for evaluating the device under test. The auxiliary function signal is generated in response to one or more timing signals produced by the timing circuitry after it has counted another selected number of oscillator pulses.
To start a new testing sequence, the various components of the testing system are initialized, as necessary, in response to initializing signals. Preferably, initializing signal circuitry generates the initializing signals in response to one or more timing signals produced by the timing circuitry after it has counted a selected number of oscillator pulses.